The Evolution of Sex Differences in
Language, Sexuality, and Visual Spatial Skills
Rhawn Joseph, Ph.D.
Brain Research Laboratory
SEX DIFFERENCES IN SEXUAL BEHAVIOR
The human female has a greater sexual capacity that the human male. She can experience up to 50 orgasms in just a few hours and her orgasms are more intense as compared to the human male (Masters and Johnson, 1966).
Unlike other female primates and mammals, the human female is able to have sex at all times which makes her the sexiest female on the planet. However, like her primate cousins whose face and genitals become redish or pink and who secrete sexual pheromones, the human female signals her sexual availability by applying rouge and scent, and she has evolved an enlarged derrier and swollen breasts--which, in other primates, signals sexual receptivity.
Like other social primates, on "average" the human female has more sex partners than the "average" male and she tends to become sexually aroused by other "sexy" females (Joseph, 2000).
According to the 1998 report of the International Labor Organization (1998) and the Coalition Against Trafficking in Women (Hughes, 2000), over 200 million women world wide work as prostitutes and have sex with over 5 men a "working" day. In fact, as a man can ejaculate within a matter of minutes, a prostitute working in a busy brothel may have sex with up to 5 men in just a few hours. As reviewed by Joseph (2000) a prostitute may have sex with an estimated 694 to 1000 (or more) men a year and with over 5,000 men during their career. The average male has fewer than 10 sex partners in a life time.
In some countries up to 30% of young adult females work as prostitutes, with the sex industry accounting for up to 14% of the gross domestic product (International Labor Organization, 1998; Hughes, 2000). In Indonesia, for example, the gross income from prostitution is around 3.6 billion dollars, whereas in Thailand the income is almost 27 billion dollars annually (Hughes, 2000; International Labor Organization, 1998). Thus based on labor statistics and the income generated, it appears that world wide over 200 million women, over 10% of the adult female population, have sex with 694 to over 1000 men a year. And, the majority of these women probably have sex with over five thousand men each, during the course of their working career. Although it is true that a few professional athletes and male movies stars have claimed to have had sex with thousands of women, these males are the exception as most males instead tend to report (on average) fewer than 10 sex partners in a life time (Davis & Smith, 1994; Greer & Buss, 1994; Kinsey et al., 1953; Laumann et al., 1994; Sprecher & MecKinney, 1993; Valois et al., 1997).
As reviewed by Joseph (2000) females become infected with sexually transmitted diseases at a rate 2.5 to 5 times that of males, which suggests a relatively larger percentage of females are having sex with a relatively smaller percentage of males. A review of the animal literature also indicates non-human females have more sex partners, on average, as compared to males. Females of many species, including humans, preferentially and repeatedly mate with (a relatively small percentage of) high status males while refusing sex with (the relatively higher percentage of) low status males.
SEX DIFFERENCES IN COGNITION
It is well established that human females excel over males across a variety of language and articulatory-related tasks (Bayley, 1968; Broverman et al., 1968; Harris, 1978; Koenigsknecht and Friedman, 1976; Hampson and Kimura 1992; Harshman et al., 1983; Hyde and Lynn, 1988; Kimura, 1993; Lezak, 1983; McGlone, 1980; McGuiness, 1976; Moore, 1967). Human females produce more social-emotional vocalizations (Brody, 1985; Burton and Levy, 1989; Gilbert, 1969; Joseph, 1993, 1999e; Tannen, 1990), and when in all female groups or pairs, they tend to talk faster and to mutually vocalize more than males in all male groups or pairs (Glass, 1993; Joseph, 1993; Tannen, 1990) and to vocalize more and more rapidly when with a male with whom they are familiar (Joseph, 1993). Based on unpublished word counts conducted by this author, it has been found that females produce 4 more words on average, than males, per five seconds of dialogue.
Likewise, female monkeys and apes and primate mothers and female infants vocalize more frequently and more frequently engage in mutual social vocalizations (e.g. Cross and Harlow, 1965; Erwin, 1980; Mori, 1975; Mitchell, 1979). Primate mothers and daughters (e.g. chimpanzees) engage in mutual vocalizations and remain physically close throughout their lives and mothers typically have several successive daughters or sons thus forming mutually vocalizing family units.. Even female dogs vocalize (bark) more often and for longer time periods (especially in response to other dogs) than males (unpublished observations).
By contrast, male primates (e.g. chimpanzees) although more noisy and boisterous especially when congregating together, are more independent and tend to wonder off alone. They also tend to vocalize predominantly when threatening other males or females, and when excited, frightened, engaged in dominance displays, or following a successful sneak attack on chimps from a neighboring troop (e.g. Erwin, 1980; Fedigan, 1992; Goodall, 1986, 1990; Mitchell, 1979). Indeed, although male chimps move quietly for hours in search of a victim, after one these attacks, they will hoot, scream, and beat on trees.
Hence, these trends toward a greater female facility for mutual social emotional vocalizing (especially to maintain relationships) and the male trend toward vocalizing and to make more noise in order to establish dominance (e.g., in humans, roaring their turbo charged engine) were well established long before the emergence of modern H. sapiens sapiens.
Conversely, it is well established that human males excel over females across a variety of visual-spatial problem solving and perceptual tasks (Broverman et al., 1968; Harris, 1978; Joseph, 1993, 1999e; Kimura, 1993; Linn and Petersen, 1985; Thomas et al., 1973). Visual-spatial superiorities, however, are also demonstrated by other species including male rats (Dawson et al., 1975; Joseph 1979; Joseph and Gallagher, 1980; Joseph et al., 1978).
It is apparent that these same cross-species sex differences have become more pronounced in humans. However, rather than purely a product of societal, political, or parental pressures, the amplification of these sex differences, like other cognitive capabilities such as math, are also neurologically based and a product of our evolutionary-environmental heritage. This includes the differential environmental pressures exerted on males and females and their descendants over the course of the last million years, possibly reaching their culmination with the close of the Upper Paleolithic (Joseph, 1993, 1999e).
FROM HOMINOID TO HOMINID
CHIMPANZEES & AUSTRALOPITHECUS
The human female shares numerous sexual, cognitive, emotional, and behavioral characteristics with other species, the chimpanzee in particular (Bygott,1979; de Waal, 1989; Goodall, 1986, 1990; Itani & Suzuki, 1967; McGrew, 1981; Tanner, 1981, 1987; Stanford, 1998).
For example, although there is considerable variation, the sexual behavior of the female human (Gold & Burt, 1978; Matteo & Rissman, 1984; Udry & Morris, 1968, 1970; Wolfe, 1991) and the female chimpanzee (Fedigan, 1992; Michael, 1972) increases at the time of ovulation, that is, at midcycle; though in humans there is a second peak just before and after menstruation (Fisher, 1973).
Moreover, human and group living (multi-male/female) hominoid females are capable of experiencing multiple orgasms (e.g., Allen, and Lemmon, 1981; Burton, 1971; Chevalier-Skolnikoff, 1974; Goldfoot et al., 1980; Masters & Johnson, 1966; Michael et al., 1974) and commonly (though there are exceptions) have sex with multiple partners. Multiple sex partners ensures she will become pregnant, and multiple orgasms reward her with increasing pleasure as she sexually dallies with male after male.
These and other female chimpanzee/human commonalties appear to be due to a common genetic and evolutionary heritage and the sexual differentiation of the limbic system. It is this ancestral hominoid heritage and limbic system commonalties which explains not only her capacity for multiple orgasms, but the fact that the human female's "monthly rhythm of ovogenesis, ovulation, estrogen and progesterone secretion, uterine stimulation, and menstrual bleeding follows the basic primate pattern" (Beach, 1974, p. 356). Because they share common ancestors and a limbic system organized in a "female" pattern, female chimps and humans are sexually similar.
The human female sometimes behaves like, and biologically, in many respects is similar to a female chimpanzee in heat. This is not only because we share a common ancestor, but because our most distant "human" ancestors were essentially apes. Indeed, given these primate origins and commonalties, the initial evolution of the human females' unique sexuality is therefore best understood from a pongid perspective, beginning with Australopithecus, and later, H. habilis, whose social life was probably more ape-like than human-like.
The common ancestors for chimps and humans diverged 5 million year ago and the chimpanzee brain (395-410 cc) is just slightly smaller than the average Australopithecus brain (375-440 cc). Male chimps are also about 20% larger than females. Given these and the other genetic and sexual similarities mentioned above, it can be assumed that social-sexual and consort relations between ancestral males and females were more like that of chimpanzees.
And, being more ape-like than human, it can also be inferred that these first pre-human females, i.e., australopithecus, were extremely sexually promiscuous, and probably had sex up to fifty times a day when they entered estrus. Like other social apes, our pre-human female australopithecine/habilis ancestors probably had sex with every desirable and high status male of the troop, and she likely snuck off to an adjacent troop where she would then enjoy a romantic vacation by again having sex up to fifty times a day with every desirable and high status male--a common behavior of female chimps.
HOMO ERECTUS: SEXUALITY AND THE HOME BASE
There is no general agreement as to the various phylogentic relationships shared by the wide variety of Plio-pleistocene hominids so far discovered (Leakey, 1994; Skelton and McHenry, 1992), and it is not yet established if present-day humans descended from Australopithecus, Homo habilis, or both (Grine, 1988; Leakey and Walker, 1988; McHenry and Berger, 1998; Skelton and McHenry, 1992). Nevertheless, following H. habilis and Australopithecus were a wide range of quite different individuals collectively referred to as Homo erectus.
Homo erectus were big and robust, with thick browridges, large teeth, and bulging shoulder muscles (Day, 1996; Potts, 1996; Rightmire, 1990), and ranged throughout Africa, Europe, Russia, Indonesia and China from approximately 1.9 million until about 300,000 years ago, with a few isolated populations possibly hanging on in the island of Java, until 27,000 years B.P. (Day, 1996; Potts, 1984, 1996; Rightmire, 1990; Swisher et al., 1996). Presumably, H. erectus is the common ancestor for Neanderthals and modern humans.
About 1.5 million years ago H. erectus learned to harness fire and by 500,000 B.P., the first hearths began to appear in China, France, Hungary and elsewhere (Clark & Harris 1985; Isacc, 1982; Rightmire, 1990). By 500,000 B.P. H. erectus was regularly constructing crude shelters and home bases (Clark and Harris 1985; Potts 1984, 1996; Rightmire, 1990; Zhang, 1985); achievements that may have coincided with a major change in female sexuality (see chapter 8).
For example, and as is well known, during the transition from Hominoid to hominid, the vaginal canal underwent a reorientation which enabled males and females to face one another during sexual intercourse, thus promoting interpersonal intimacy. With the exception of the Bonobo who are more variable, all other primates and non-human animals generally assume a dorsal ventral posture when mating (Ford and Beach, 1951; Goodall, 1986, 1990; Wickler, 1973).
Based on the evidence reviewed in chapter 8, this vaginal reorientation may have coincided with alterations in the H. erectus pelvis and the emergence of full time female sexuality receptivity. That is, with the evolution of H. erectus the female estrus cycle and the hominoid menstrual cycle which generally dictates sexually receptivity, may have undergone a transition such that, unlike all other (non-captive) female species, but like modern day woman, the H. erectus female became sexually receptive at all times. However, like modern woman (Masters and Johnson, 1966) and many other female mammals and primates such as the chimpanzee (Ford and Beach, 1951; Goodall, 1986, 1990), she likely retained the capacity to enjoy multiple sex partners (and to experience multiple orgasms) one after another.
It has also been inferred, based in part on the evidence reviewed below, that the breasts and buttocks of the human female may have become permanently enlarged during this evolutionary time period, serving to continually signal her new sexual status and availability. Indeed, these same sexual signals are employed by other species when in estrus. For example, some female primates, such as the gelada baboon, advertise their sexual status via sexual swellings of the chest nodules which flush red (Fedigan, 1992; Jolly, 1972). These nodules form a necklace-like pattern which mimics the pattern of her rump--an enlarged derriere being a common sexual advertisement among many species (see below).
Moreover, female rhesus monkeys have been observed to pull and suck on their own nipples when they enter estrus and to display them to potential consorts (Carpenter, 1942), and others, such as the male baboon, will lip smack on the female's teats, presumably as a sign of affection (Ford and Beach, 1951). In fact, it is not uncommon for the swollen teats of the female primate to serve as a social signal, to decrease aggression or to promote bonding and feelings of security (Eible-Eibesfelt, 1990; Wickler, 1973). However, in these latter instances, the female is usually lactating.
By contrast, human females are the only animal on this planet who possess breasts which remain enlarged even when she is incapable of nursing or producing milk or becoming impregnated. In other primates, if the teats swell, turn red, or enlarge, it is only when she is in estrus or lactating. Moreover, the nipples of the human female will grow and stiffen, and the breasts will expand by almost a third when she becomes sexually aroused (Masters and Johnson, 1966) thus signally her sexual interest.
Indeed, human females not uncommonly artificially exaggerate the size of the breasts so as to emphasize her possible sexual availability and to attract male sex partners and women who have breast enhancement surgery have nearly three times as many sex partners as women who don't including a greater incidence of terminated pregnancies (Cook et al., 1997). Hence, it can be concluded that over the course of human evolution the female breast increased in size so as to signal her continual sexual availability.
If these great changes in sexual status and the development of secondary sexual attributes occurred during the rein of H. erectus, it likely contributed to the development of long term male-female mating relationships as is suggested by the creation of the home base and semi-permanent shelters. For example, among chimpanzees, its not uncommon for a dominant male to threaten and physically force a high status estrus females to accompany him away from the troop, and to establish a home base where he provides her with an inordinate amount of attention; that is, until she ceases to be sexually receptive at which point he loses interest and returns to the troop (Goodall, 1986, 1990).
Likewise, when the human female became continually sexually receptive, and continually advertised this fact, this may have motivated some human males to respond in a similar fashion and to form a long term mating relationship and to establish a personal home base, as is common among modern humans. Although a few other species mate for life, and/or limit their seasonal breeding to one mate, with the exception of gibbons, and some New World monkeys, this is not the case with other primates or most mammals, and is true in less than 1% of birds (Kleiman, 1977; Stacey, 1982; Wickler, 1973).
Hence, the emergence of full time sexual receptivity (and associated physical changes) likely contributed to the formation of the home base, long term mating relationships (or at least serial monogamy), and perhaps even the first "families." The development of full time sexual receptivity and accompanying changes in the breasts and buttocks (see below) may also explain why H. erectus (or archaic H. sapiens) began utilizing various earth pigments (ochre), possibly for artistic or cosmetic purposes, or to emphasize female sexual availability. In one site, lumps of red ochre, many pointed like pencils, were found (Rightmire, 1990); and redness of the female primate genitalia is an obvious signal of sexual receptivity.
EVOLUTION OF FEMALE PELVIS AND THE "BIG BRAIN"
It was during the latter stages of H. erectus evolution that the brain became significantly enlarged. The brain in fact doubled in size with the transition from Australopithecus (440 cm3) to H. erectus (937 cm3), approaching within 15% of present-day humans (Conroy 1998; Potts, 1996; Rightmire, 1990; Tobias, 1971). However, with the advent of the big brain, human sex differences, including those related to full time female sexuality receptivity appear to have become even more pronounced.
Because a bigger brain comes in a bigger head, this required a larger birth canal and an increase in the sexual physical differentiation in the size and width of the H. erectus (and modern) female pelvis so as to accomodate the birth of a big brained baby (Day, 1996; Jacob, 1973; Potts, 1996; Rightmire, 1990; Riscutia, 1973). Specifically, with the evolution of a bigger brain and with the transition from Australopithicus to H. habilis to H. erectus, the pelvic opening became longer and more round and ovoid (see Figure 1) as it expanded from front to back (Day, 1982, Lovejoy, 1988; Sigmon, 1982); changes with made birth more difficult as now the infant's head had to rotate as it passes down the birth canal in order to emerge from the pelvic opening. As with modern woman, this adaptation likely forced the female erectus' upper legs wider apart and her knees closer together, thus altering her gait and balance, causing her to wiggle her derriere when walking. Presumably, this alteration, coupled with the evolution of new muscles to aid in the upright stance, accentuated and drew attention to the female derriere and her sexual availability (Joseph, 1993; see Figures 2,3,4); a sexual-social signal accentuated in modern women through high heels and tight clothes, and in the last century, via the bustle, hoop skirts and in previous centuries dresses designed to grossly exaggerate the width of the hips (Wickler 1973).
These same sexual signals are characteristic of other primates (Ford and Beach, 1951; Wickler, 1973). When female chimps and other apes and monkeys enter estrus, their dorsally oriented genitals/vaginal lips turn pink or a bright crimson and balloons outward, and in fact becomes so huge and distended they have difficulty sitting down. Moreover, estrus chimps and other primates, including baboons and the gorilla, go to great lengths to focus male attention on her buttocks, which she may flaunt and display by swaying them "enticingly" (Fedigan, 1992; Ford and Beach, 1951; Goodall, 1986, 1990; MacKinnon, 1979; Nadler, 1976; Wickler, 1973). As detailed in chapter 8, the female genitalia and a derriere that is swollen or emphasized are obvious sexual signals which are employed to solicit male sexual attention. Likewise, modern human females accentuate and call attention to the derriere by wearing tight skirts and high heels which emphasizes the buttocks by puffing it out. When attired in this fashion she is assuming a sexually receptive posture and continually advertising her sexual availability.
The transformation of the human female hips and pelvis, however, also limited her ability to run and maneuver about in space, at least, as compared to most males (Day, 1996). This is because, be it H. erectus or modern H. sapiens sapiens "these changes are less pronounced in the... male pelvis" (Lovejoy, 1988, p. 123). "The size of the canal in men is controlled mainly by locomotor, not reproductive factors" (Campbell, 1985, p. 152).
Moreover, her pelvis became more fragile (e.g., Comas, 1960) and subject to fracture if stressed by continous hard running and jumping. This condition plagues even female soldiers who suffer an unusually high incidence of pelvic and leg fractures although their training and duties are not as strenuous or arduous as males (1995 U.S. Marines Report, Paris Island). The female pelvis is in fact less massive, lighter and thus weaker than the male pelvis (Comas, 1960, p. 337). Moreover, as the human femoral neck expanded and became longer so as to accommodate these changes in the pelvic girdle, it became more porous and thus weaker (Lovejoy, 1988) as well as subject to stress related injury due, in part, to the greater transverse and sagittal diameter of the female pelvic inlet (Comas, 1960, p. 337).
As summarized by Day (1996, p. 5), "The female bony pelvis is a compromise between the needs of childbirth and those of locomotion with heavy selection pressure on the need for successful reproduction. The male pelvis, with no reproductive function to parallel that of the female, evolved for efficiency in bipedal locomotion." This helps "explain the differences in peak achievements between men and women in running and jumping."
Hence, be it modern woman or female H. erectus, in accomodating the birth of big brained babies, these physical changes not only advertised her sexual status, but likely interfered with her ability to endure and keep up with males on their long hunting sojourns; a function also of her reduced upper body strength and the prolonged dependency of her big brained babies (Day, 1996; Joseph, 1993, 1999e; Lovejoy, 1981; Murdock and Provost 1973). As such, with the evolution of H. erectus (and their descendants), males and females became increasingly specialized to perform certain tasks, e.g. hunting versus gathering--a division of labor characteristic of all hunting and gathering groups (Dahlberg, 1981; Hiatt, 1970; Martin and Voorhies, 1975; Murdock and Provost, 1973; Zilman, 1981) including chimpanzees (Goodall, 1990).
THE EVOLUTION OF THE DIVISION OF LABOR: HUNTERS AND GATHERERS
THE HUNTING HOMO ERECTUS
Female primates, including chimps (whose activated DNA is 98.6% identical to human DNA), sate their hunger, and that of their infants, through systematic gathering of foodstuffs and insects, most of which is shared with their young (Goodall, 1990). Although male primates gather, they also hunt and become exceedingly excited when killing not only other animals (Hamburg, 1971; Harding and Strum, 1978), but other primates including former members of their troop who they may ambush and beat to death (Goodall, 1986, 1990). Be it other animals or a chimp from a neighboring band, the entire troop will gather and excitedly beg for a tiny morsel of the bloody flesh (Goodall, 1986).
Be it human, non-human primate, or mammal, males tend to be violent (Elia, 1988; Fedigan, 1992; Goodall, 1986, 1990; Hamburg, 1971; Johnson, 1972; Lorenz, 1966; Manning, 1972; Mitchell, 1979; Moyer, 1974), and the male proclivity to hunt appears to be direct extension of these proclivities (Joseph, 1993, 1999e). Indeed, over 80% of all violent crimes and murders are committed by human males (Uniformed Crime Reports, 1990-1996). Likewise, male chimpanzees initiate attack five times as frequently as females and are responsible for 90% of all aggressive encounters (Bygott, 1979; Van Lawick-Goodall, 1968).
Sex differences in violence and belligerence are apparent as early as the first two months of life even in chimps and other primates (Ransom and Rowell, 1972; Mitchell, 1979). Indeed, the primate/human (male) tendency toward violence may well have been demonstrated millions of years ago by Australopithecus who not only hunted small animals, but possibly each other. According to Dart (1949), Australopithecines "were confirmed killers; carnivorous creatures that seized others by violence, battered them to death, tore apart their broken bodies, dismembered them limb from limb, and slaking their ravenous thirst with the hot blood of the pitiful victims and greedily devouring their writhing flesh." Although Dart's conclusions have been challenged, as noted above, male chimps not uncommonly engage in violent, murderous and even cannibalistic interactions with other troop member (Goodall, 1986, 1990).
Like modern humans, gangs of male chimpanzees will also engage in surprise attacks on neighboring colonies, beating and killing the old, infirm, and young alike, including former friends; even drinking their blood. That Australopithecus were killers and hunters of meat, thus, should not be surprising. In fact, from an examination of Australopithene teeth it is apparent that these were meat eaters whose diet also consisted of vegetable matter (Sponheimer & Lee-thorp, 1999)--as is the case of modern hunting gathering groups (Dahlberg, 1981; Lee and DeVore, 1968; Martin and Voorhies, 1975; Murdock and Provost, 1973; Zilman, 1981) and chimpanzees.
Specifically, from an analysis of the tooth enamel of Australopithecus africanus, it was determined that these individuals ate food rich in carbon 13--that is high protein food (Sponheimer & Lee-thorp, 1999). As these teeth were lacking the telltale scratches associated with vegetable matter, it can thus be concluded they were eating meat, i.e., grass eating animals, as well as vegetable matter.
Moreover, the remains of A. garhi were found in association with antelope leg bones which show the signs of cutting and pounding by a shark and blunt rock (White et al., 1999). Hence, it is fairly obvious that these were meat eaters and probably killers of animals and each other, as is the case with chimpanzees.
Thus sex differences in aggression and trends in the division of labor had probably been established with the evolution of hominoids (as is suggested by modern day chimps), and likely continued to develop with the emergence of Australopithecus. These same trends, however, were likely exaggerated with the evolution of the big brained H. erectus.
A bigger, more complex brain confers upon the bearer increased cognitive and intellectual capabilities, and the male H. erectus employed that greater intelligence in the pursuit of bigger game, including deer, bisons, horses and even bear and elephant (Potts, 1996; Rightmire, 1990). His killing technique, however, remained rather primitive. He would either surround his prey and stone them to death, or would use fire to frighten and stampede all manner of animals over cliffs or into swamps, typically killing more animals than could possibly be eaten (Potts, 1996; Rightmire, 1990).
Hunting, however, does not require language (Joseph, 1993, 1999e). Rather, successful hunting requires prolonged silence, excellent visual-spatial and gross motor skills, and the capacity to endure long treks in the pursuit of prey. These are abilities at which males excel, including modern H. sapiens sapiens (Joseph, 1988a, 1999e). As detailed below, it is not until the emergence of modern (Upper Paleolithic) H. sapiens sapiens, that "modern language evolved.
THE MATERNAL H. ERECTUS
Just as primate males hunt whereas most primate females are not so inclined, it is unlikely that the female H. erectus, burdened by pregnancy, crying children, and her fragile pelvis and awkward gait, would have behaved otherwise. Rather, whereas most primate males, including male humans tend to have little interest in infants or caring for the young (Belsky et al., 1984; Clarke-Stewart, 1978; Frodi et al., 1982) it is likely that the female H. erectus, like other female primates, would have pursued her own inclinations including the desire to bear babies and nurture the young.
In fact, be it chimpanzee, baboon, rhesus macaque, or human, females demonstrate an extraordinary interest in babies and will engage in play-mothering during even the earliest phases of their own childhood (Berman, 1983; Berman and Goodman, 1984; Blakemore, 1981, 1985, 1990; Devore, 1964; Elia, 1988; Fedigan, 1992; Frodi and Lamb, 1978; Goodall, 1971, 1990; Jolly 1972; Kummer, 1971; Melson and Fogel, 1982; Mitchell, 1979; Nash and Fledman, 1981; Strum 1987; Suomi, 1972; Zahn-Waxler et al., 1983).
Female humans (Ainsworth and Wittig, 1969; Berman, 1983; Blakemore, 1990) and non-human (group living) female primates will eagerly cuddle, groom, and hold babies that are not their own (Jolly, 1972; Devore, 1964; Kummer, 1971, Strum, 1987; Suomi, 1972; Mitchell, 1979; Goodall, 1971). Although there are exceptions such as the pigtail macaque (Fedigan, 1992; Kaufman, 1974), in general, female humans, apes, or monkeys with babies, become the center of female-attention (Elia, 1988; Fedigan, 1992; Jolly, 1972, Mitchell, 1979, Strum, 1987).
By contrast, human men and boys and non-human male primates have little interest in babies or young children and generally provide little or no nurturant care even for their own offspring though they may form alliances with siblings (Fedigan, 1992; Kummer, 1968, 1971; Mitchell, 1968, 1979, Goodall, 1971; Gordon and Draper, 1982; Rossi, 1985; Rowell et al., 1968), one of the few exceptions being owl monkeys, and to a lesser extent, baboons (Devore, 1977; Fedigan, 1992; Kummer, 1968). Human males and fathers rarely behave in any manner that approximates normal female maternal behavior (Belsky et al., 1984; Clarke-Stewart, 1978; Frodi et al., 1982). As noted, males tend to be aggressive and violent and the desire to nurture infants may not be compatible with these tendencies. Indeed, males are responsible for over 70% of all murders involving infants and children (U.S. Justice Dept. 1996-1997). Likewise, among many other primates (gorillas, Barbary apes, and rhesus, howler, and red-tailed monkeys) males stereotypically kill infants not their own (Fedigan, 1992; Hrdy, 1979).
THE INFANT-MATERNAL ROOTS OF EMOTIONAL LANGUAGE
Considerable vocalizing occurs between mothers and infants (reviewed in Barnett, 1995). The infants of many species will often sing along or produce sounds in accompaniment to those produced by their mothers (Bayart et al., 1990; Jurgens, 1990; Wiener et al., 1990). These interactions reinforce and promote mutual vocalization, attachment, and contribute to survival. Hence, the first forms of complex social-emotional communication may have been produced in a maternal context (Joseph, 1993, 1999e; MacLean, 1990), and as in non-human animals, were limbic in origin (Joseph, 1992b).
Because the big brained infant H. erectus likely required long term care, it can be assumed that there was an impetus for female H. erectus to vocalize with her young for years at a time. Indeed, a big brain requires more time to grow and mature, which in turn results in prolonged immaturity and helplessness. In consequence, the female tendency to vocalize more than males may have been given additional impetus well over 500,000 years ago.
Among most social animals and gathering groups, the production of sound is very important in regard to infant care. If an infant becomes lost, separated, or in danger, this is best conveyed via a cry of distress and fear; cries which would cause a mother to come running to the rescue. Conversely, vocalizations produced by the mother and her co-gatherers enable an infant (or a lost gatherer) to orient and find its way back if perchance it got lost or separated. In this regard, the tendency to vocalize may have ensured for breeding success.
Among animals, and present day human mothers, much of this initial mutual sound production is emotional and prosodic (Cooper and Aslin, 1990; Fernald, 1991, 1992; Fernald et al., 1989; Jurgens, 1990) and constitutes what has been referred to as "limbic language" (chapter 15). Emotional sound production is mediated by the amygdala, cingulate gyrus, and other limbic and subcortical nuclei, but is also hierarchically represented in humans and produced and perceived by the right frontal and right temporal-parietal area. These emotional-language areas appear to be more extensively developed in human females (see below). By contrast, the denotative, and vocabulary-rich grammatical components of modern human speech are mediated by the left frontal and temporal-parietal area; i.e. Broca's and Wernicke's speech areas and the inferior parietal lobule.
Because infants are emotionally oriented and have little or no understanding of non-emotional speech, these mutual mother-infant vocalizations usually consists of exaggerated emotional prosody (Cooper and Aslin, 1990; Fernald, 1991, 1992, 1993; Fernald et al., 1989). Indeed, human infants prefer listening to and are more responsive to these exaggerated emotional vocalizations, particularly when produced by a female (Cooper and Aslin, 1990). Moreover, human (and non-human) females demonstrate superiorities in this regard, and not only produce more mutual social-emotional vocalizations than males (Brody, 1985; Burton and Levy, 1989; Gilbert, 1969; Glass, 1992; Tannen, 1990) and more words in five seconds of conversation, but tend to employ 5-6 different prosodic variations and utilize the higher registers when conversing (Joseph, 1993). They're also more likely to employ glissando or sliding effects between stressed syllables (Brend, 1975; Coleman, 1971; Edelsky, 1979).
Men tend to be more monotone, employing 2-3 variations on average, most of which hovers around the lower registers (Brend, 1975; Coleman, 1971; Edelsky, 1979). Even when trying to emphasize a point males are less likely to employ melodic extremes but instead tend to speak louder.
Although influenced by sex differences in the oral-laryngeal structures, these differential vocalizing abilities are also reflected in the greater capacity of the female brain (and right hemisphere) to express and perceive emotional vocalizations (Burton and Levy, 1989; Hall, 1978; Soloman and Ali, 1972). This superior sensitivity includes the ability to understand, perceive, and express empathy and social-emotional nuances (Burton and Levy, 1989; Brody, 1985; Buck, 1977, 1984; Buck et al., 1974, 1982; Card et al., 1986; Eisenberg et al., 1989; Fuchs and Thelan, 1988; Harackiewicz, 1982; Kemper, 1978; Lewis, 1983, Rubin, 1983; Safer, 1981; Shennum and Bugental, 1982; Soloman and Ali, 1972; Strayer, 1980) and a greater willingness to express emotional issues and discuss personal problems (Gilbert, 1969; Gilligan, 1982; Lutz, 1980; Walker et al., 1987; Lombardo and Levine, 1981).
Witness, for example, the wife of President Clinton, discussing and explaining in the August, 1999 issue of a national magazine for women--aptly named "TALK"--that her husband was "scarred by abuse" as a child, as well as numerous other personal details regarding his life, his mother, his grandmother, his alcoholic step-father, and his childhood. And she details this while he is still President, and did so, she explains, so as to form a connection and feel closer to the voters.
In fact, from childhood to adulthood, females appear to be much more emotionally expressive than males (Brody, 1985; Burton and Levy, 1989; Gilbert, 1969; Tannen, 1990), who in contrast have difficulty discussing personal difficulties or expressing their emotions other than through anger, happiness, and sexual arousal (Balswick, 1982, 1988; Goldberg, 1976; O'Neil, 1982; Joseph, 1993; Sattel, 1989; Tannen, 1990).
Therefore, like chimpanzees and present-day human females, female H. erectus probably engaged in mutual mother-infant vocalizations, and probably engaged in more mutual social-emotional vocalization not just with her children but with each other. However, as based on an analysis of H. erectus' tool technology, and the fact that it was somewhat crude and lacking in temporal sequential sophistication (though certainly a lot of time was put into their construction), it can be assumed that the brain of H. erectus was not capable of thinking in terms of complex temporal sequences (chapter 6). Hence, it can be assumed that H. erectus did not speak in the temporal sequential and grammatical manner characteristic of present-day humans. Nor is it likely H, erectus uttered complex words though some scientists have argued otherwise (e.g. Wilkins and Wakefield, 1995).
Rather, H. erectus probably tended to use gesture, body language, facial expression, as well as grunts, groans, mimicry, and the production of emotional sounds in order to convey needs, fears, feelings and desires. On the other hand, as gathering and the construction of domestic-tools was probably an ongoing female H. erectus activity (see below), these activities likely eventually gave rise to improvements in bilateral, temporal and sequential fine motor skills; thus providing what would become the neurological foundation for the development of complex grammatical, vocabulary-rich, human language.
TOOL-MAKING, TEMPORAL SEQUENCING AND LANGUAGE
Whereas the big brained male H. erectus refined his hunting techniques and became a hunter of bigger game, females refined their gathering and food preparation techniques as is suggested by the creation of crude tools such as choppers, scrapers, cleavers with a stright cutting edge on one side (Day, 1996; Rightmire, 1990), and probably digging sticks, as is characteristic of female chimpanzees (Goodall, 1990; McGrew and Marchant, 1992). That these tools were fashioned by a female hand can be deduced by their domestic use. Among hunting and gathering groups it is females and not the males who make and use tools (Niethhammer, 1977), the only exception being hunting implements and weapons of war which females are not allowed to touch (Tabet, 1982). Similarly, females chimps use food/gathering-related tools much more frequently than males (Goodall, 1986; McGrew and Marchant, 1992) who in turn are more likely to use sticks and rocks to threaten other males (Bygott, 1979; Goodall, 1990; Van Lawick-Goodall, 1968 ). As with other male primates, and given his penchant for big game hunting, it was probably the male H. erectus who created the first hand ax; a killing tool which made its appearance about 650,000 years ago (Potts, 1996; Rightmire, 1990).
As similar "gathering" versus "hunting" (and later, more advanced) tools were fashioned throughout Africa, Europe, Asia and the Middle East until around 10,000 years ago, it can be assumed, with the exception of the European Neanderthals (chapter 6), that this division of labor prevailed throughout the Middle Paleolithic, well after H. erectus was replaced by archaic H. sapiens. Males continued to hunt and kill (and to invent more efficient killing tools), whereas females cared for the young, maintained the home base, and were responsible for the gathering of food and related "domestic" activities. However, this is not to imply that females never killed small animals, or never collaborated or assisted in the hunt, as that is not the case with humans (Gusinde, 1961; Wantanabe 1964) or chimpanzees (Goodall, 1986).
By the close the Middle Paleolithic (around 30,000 B.P.), and the emergence of "modern" Upper Paleolithic H. sapiens sapiens, such as the Cro-Magnon, hunting had become the center of religious and artistic life. Nevertheless, 60-80% of the Cro-Magon diet consisted of fruits, nuts, grains, honey, roots and vegetables (Clark, 1952; Prideaux, 1973), which were probably gathered by females. Among the hunting and gathering societies in existence during the last few centurties, women have been and are the gatherers and main providers of food whereas spoils from the hunt account for only about 35% of the diet (Dahlberg, 1981; Lee and DeVore, 1968; Martin and Voorhies, 1975; Murdock and Provost, 1973; Zilman, 1981).
In grubbing for roots and bulbs the Upper Paleolithic female-gatherer probably used a digging stick which she periodically sharpened by using stone flakes. These gatherers also fashioned hammerstones for cracking nuts and grinding the produce she collected. As in recent hunting gathering groups (Lee, 1974; Murdock and Provost, 1973), her duties would include the preparation of any meats she scavenged or which the men brought home from their hunting sojourns. In addition to food preparation, clothes were sewn and fashioned out of hides (Clark, 1952, 1967; Prideaux, 1973), and these too are tasks associated with women (Gusinde, 1961; Lee, 1974; Neithhammer, 1977), including, presumably, the Cro-Magnon females of the Upper Paleolithic.
Thus the duties of the Upper Paleolithic female were much more multi-faceted and complex than her predecessors, and included cleaning hides via a scraper, drying and curing the skin over the smoke of a fire, and then using a knife or cutter to make the general desired shape. The Upper Paleolithic female was also employing a punch to make holes in these hides, through which leather straps or a vine could be passed so as to create a garment that could keep out the cold (Clark, 1952, 1967; Prideaux, 1973). They were also weaving and using a needle to sew garments together; "domestic" tasks which are almost exclusively associated with "women's" work (Murdock and Provost, 1973; Neithhammer, 1977).
The necessary skills required for tool construction and the efficient gathering of vegetables, fruits, seeds, berries and the digging of roots, include rapid, temporal-sequential fine motor maneuvers with the arms, hands, and particularly the fingers (Hamrick et al., 1998; Marzek, 1997; Susman, 1994). Similarly, most tools are made in a step-wise, temporal sequential manner, with specific fine-motor movements, and considerable precision (Bradshaw and Rogers, 1992; Greenfield, 1992; Hamrick et al., 1998; Marzke, 1997; Susman, 1994; Toth, 1985); abilities which enable the tool maker to construct the same implement over and over again. This also requires that the tool maker be in possession of a brain that can control the hand and which can use foresight and planning in order to carry out the steps involved in the implement's manufacture. In this regard, although males were also fashioners of tools (i.e. those used for killing), it is noteworthy that females tend to excel at fine motor activities, such as those involving rapid, repetitive temporal sequencing (Broverman et al., 1968; Hampson and Kimura, 1992).
These "domestic" activities, coupled with her innate tendency to engage in mutual vocalizations, and to vocalize with her young and fellow gatherers, likely coincided with, and stimulated the development of the temporal sequential neurological foundations of what would become a female superiority in the evolution of grammatical, vocabulary-rich human language. However, as the tools made by H. erectus and archaic (Middle Paleolithic) H. sapiens remained relatively crude, whereas a creative explosion in tool-making technology typifies the onset of the Upper Paeleolithic (Clark, 1952, 1967; Mellars, 1989; Prideaux, 1973), it appears that the human brain did not become fully adapted for perceiving and expressing temporal sequential, grammatically complex, vocabulary-rich language, until the emergence of the Upper Paleolithic human female. As will be detailed below, the emergence of these linguistic capabilities were promoted by and thus coincided with advances in tool technology and associated fine motor skills--activities which gave rise to the functional evolution of Broca's speech area and the angular gyrus.
THE INFERIOR PARIETAL LOBE, APRAXIA, AND TEMPORAL SEQUENCING
The angular gyrus of the inferior parietal lobule (IPL) is unique to humans (Geschwind, 1965), and is crucially evolved in controlling temporal sequential hand movements including the manipulation of external objects and internal impressions (De Renzi and Lucchetti, 1988; Heilman et al., 1982; Kimura, 1993; Strub and Geschwind, 1983). As detailed in chapter 6, the evolution of the angular gyrus enabled humans to engage in complex activities involving a series of related steps, to create and utilize tools, to produce and comprehend complex gestures, such as American Sign Language, and to express and perceive grammatical relationships--capacities which are disrupted with lesions localized to the IPL (chapter 11). In fact, the motor engrams that make possible temporal and sequential motor acts, including those involved in grammatical verbal expression, are partly localized within the IPL (De Renzi and Lucchetti, 1988; Heilman et al., 1982; Kimura, 1993; Strub and Geschwind, 1983). In fact, the IPL not only interacts with but appears to program the frontal motor areas for the purposes of producing fine motor, temporal-sequential movements, including the vocalization of speech units.
Those devoid of an angular gyrus/IPL, or those who have suffered a severe injury to this area, are generally unable to correctly manipulate or fashion complex tools -much less utilize them in a complex temporal sequence. This condition is referred to as apraxia; i.e. an inability to perform tasks involving interrelated steps and sequences (De Renzi and Lucchetti, 1988; Geschwind, 1965; Heilman et al., 1982; Kimura, 1993). With severe IPL injuries, the individual may be unable to make a cup of coffee or put on their clothes, much less fashion or sew them together. Moreover, grammatical speech is disrupted and patients may suffer extreme word finding difficulty, or a conduction aphasia. That is, speech is no longer produced as Broca's area is disconnected from the IPL and Wernicke's area (chapter 11). Likewise, reading ability is disrupted as the IPL not only comprehends and produces gestures but visual symbols including written language. Hence, the IPL/angular gyrus (including the frontal motor areas) makes possible the ability to fashion and manipulate tools and organizes speech into vocabulary-rich, temporal sequential grammatical units.
As apes do not possess an angular gyrus (Geschwind, 1965), it appears that over the course of evolution, with the development of right handedness and selective pressures acting on gene selection across gathering/tool-making generations, the IPL/angular gyrus emerged as an extension of the auditory area in the temporal lobe and the superior parietal visual-hand area. Indeed, the parietal lobes are considered a "lobe of the hand" and contain neurons which guide hand movements (Hyvarinen, 1982; Kaas, 1993; Lynch, 1980; Mountcastle et al., 1975, 1980) and which respond to visual input from the periphery and lower visual fields -the regions in which tool-making hands are most likely to come into view.
Because most individuals would use the right hand for tool making and the left for holding the tool, it is the left parietal lobe (which monitors the right lower visual field and controls the right hand) that guides and visually observes, learns and memorizes hand-movements when gathering, gesturing, or manipulating some object or constructing a tool. Over the course of evolution and as experience and the environment act on gene selection and induce neural plasticity, the parietal (and superior temporal) lobe expanded, the angular gyrus emerged, and neuroplastic alterations were induced in the adjoining motor-hand area in the frontal lobe including what would become Broca's speech area.
THE EVOLUTION OF THE SPEECH AREAS
The angular gyrus sits at the junction of the posterior-superior temporal and the occipital-parietal lobes, and is critically involved in naming, word finding, grammatical speech organization, and is in part an extension of and links Wernicke's with Broca's area (Joseph, 1982, 1999e; Geschwind, 1965; Goodglass & Kaplan, 2000; Kimura, 1993). Through its extensive interconnections with the adjacent sensory association areas, the IPL/angular gyrus receives and assimilates complex associations, thereby forming multi-modal concepts, and acts to classify and name this material which is then injected into the stream of language and thought (chapter 11). The IPL/angular gyrus, in concert with Wernicke's area, transmits this information to Broca's speech area, which in turn organizes the immediately adacent oral, laryngeal motor areas (Foerster, 1936; Fox, 1995; Joseph, 1992, 1999a).
However, primates not only lack an angular gyrus, but a functional Broca's area. Among non-human primates, the left frontal lobe, including the tissues homologous to Broca's area, does not subserve speech or vocalization (Jurgens et al. 1982; Myers 1976). Rather, vocalization in primates and other non-human mammals, is the province of the limbic system and brainstem; e.g. the cingulate gyrus, amygdala, hypothalamus, and periaqueductal gray (Joseph, 1993; Jurgens, 1990; MacLean, 1990; Robinson, 1967; 1972), and has a non-segmented organization, consisting of moans, screams, barks, grunts, pants, and pant-hoots (Erwin, 1975; Fedigan, 1992; Goodall, 1986, 1990; Hauser, 1997).
Thus, although damage to Broca's area in humans results in a profound expressive aphasia, similar destruction in non-human primates has no effect on vocalization rate, the acoustical structure of primate calls, or social-emotional communication (Jurgens et al. 1982; Myers 1976). Rather, in primates, "Broca's area" is directly involved in manual activity (Rizzolatti, et al. 1988), and the neural pathways linking the primate IPL with the homologous primate "Broca's area" are only weakly developed (Abolitiz and Garcia, 1997).
By contrast, ninety percent of primate auditory cortex neurons are activated by species-specific calls (Newman & Wollberg 1973), whereas destruction of the left superior temporal lobe disrupts that ability to make sound discriminations (Heffner & Heffner 1984; Hupfer et al. 1977; Schwarz & Tomlinson 1990). Moreover, asymmetries in the planum temporal are apparent in chimpanzees (Gannon 1998), and the primate left hemisphere has also been shown to be dominant for the perception of primate vocalizations (Hauser & Anderson 1994; Peterson & Jusczyk 1984; Peterson et al. 1978).
Presumably, left planum temporal and hemisphere dominance for vocal perception and comprehension gradually increased in the transition from Australopithecus, to H. habilis, to H. erectus, to Neanderthals. As first proposed and detailed elsewhere (Joseph, 1993, 1999e) as Wernicke's area, the parietal-hand areas and the IPL expanded, merged, and collectively gave rise to the angular gyrus, auditory input began to be sequenced, and Wernicke's area became specialized for perceive and comprehending language units. In addition, the arcuate fasciculus axonal pathways leading from the IPL to Broca's areas also significantly expanded and increased in density, and Wernicke's area became tightly linked with and began transmitting auditory-linguistic signals to Broca's area thus inducing neurplastic alterations in these tissues.
Hence, Wernicke's area began sequencing auditory input, and Broca's area was transformed from a hand area to a speech area and ceased to control hand movements. Instead Broca's area began to organize the adjacent primary motor oral-laryngeal areas so as to express the words and sentences transmitted from the IPL and Wernicke's area.
Moreover, as the right and left frontal vocalization areas are richly interconnected with the anterior cingulate vocalization centers, wheras the temporal lobe is tightly linked with the amygdala, once these neural-plastic transformation took place, "limbic language" (emotional speech) became hierarchically represented, yoked to the neocortex and subject to fractionization, temporal sequencing, and multi-classification (Joseph, 1999d,e). Wernicke's area was now able to communicate with Broca's area, with the angular gyrus injecting temporal sequences and assimilated associations into the stream of language and thought.
Hence, in addition to manipulating tools in a temporal sequential fashion, the evolution of the IPL/angular gyrus enabled humans to manipulate the internal environment and to transmit linguistic impulses to the frontal motor areas controlling the oral-laryngeal musculature, thereby reorganizing Broca's area in order to vocalize units of speech.
However, as based on an analysis of tool technology, it can be concluded that Australopithecus, H. habilis, H. erectus, and Neanderthals did not possess the neurological sophistication for vocalizing complex human language, and had not yet evolved an angular gyrus or a functional Broca's area (chapter 6). Rather, the evolution of modern speech likely corresponded to the evolution of the Upper Paleolithic female gatherer and tool maker.
THE FEMALE BRAIN & THE UPPER PALEOLITHIC
The frontal motor area representing the hand is immediately adjacent to and intimately interconnected with the primary motor areas mediating oral, laryngeal, and mandibular movements, including Broca's area (chapter 11, 19). Hence, manual activity, right handedness and expressive speech are directly related (Bradshaw and Rogers 1992; Corbalis, 1991; Hicks, 1975; Joseph, 1982; Kimura, 1993; Kinsbourne & Cook, 1971), which is why when speaking, humans commonly gesture with the hands, the right hand in particular. However, it was not until the late Middle Paleolithic that up to 90% of Paleolithic Humans may have become right handed (Cornford 1986). Similarly, it was not until the Middle to Upper Paleolithic transition, 35,000 years ago, that tool making became literally an art and complex multifaceted features were incorporated in their construction and utilization (Chauvet et al., 1996; Leroi-Gourhan, 1964, 1982; Mellars, 1989, 1996).
The Middle/Upper Paleolithic transition is characterized by the creation of complex bone tools, the sewing needle, and personal adornments such as carefully shaped beads of bone, ivory and animal teeth, animal engravings, perforated shells, statuettes, drawings, and paintings of animal and female figures (Chauvet et al., 1996; Clark, 1967; Leroi-Gourhan, 1964; 1982; Mellars, 1989).
As the creation and wearing of personal adornments, and domestic tool construction and use is associated with the human female, and as tool making and gathering often involves both hands (albeit the right more than the left), it might be expected that the human female frontal-parietal areas may have functionally evolved in a manner different from men. That is, both the left and right half of the female brain may have become organized for producing motor sequences and grammatically complex vocabulary rich speech. Moreover, as the parietal lobe and IPL/angular gyrus act on and program the frontal motor and speech areas (De Renzi & Lucchetti 1988; Heilman et al., 1982; Kimura 1993; Strub & Geschwind 1983), it might be expected that sex differences would be more pronounced in Broca's and the parietal areas. In fact, Broca's area appears to be larger in the female.
Moreover, the posterior corpus callosum which interconnects the right and left parietal lobes, appears to be significantly larger in women than men (see Holloway et al., 1993, for evidence pro and con), whereas language appears to be represented in the right half of the female to a greater degree than it is represented in the right half of the male brain (Bradshaw et al., 1977; McGlone, 1980; Shaywitz et al., 1996) --a sex difference which may also account for her superior language capabilities but also her relatively inferior visual-spatial abilities (due to functional crowding). Left hemisphere dominance for verbal functioning and right hemisphere language (and greater emotional language) representation coupled with the enhanced ability of the right and left female-IPLs to communicate via the corpus callosum, may account for why women (versus men) are less likely than men to become aphasic with a left parietal lesion (Kimura, 1993; Mateer et al., 1982); i.e. women have language-related brain tissues in reserve and are able to continue talking so long as Broca's expressive speech area is uninjured.
SEX DIFFERENCES IN LANGUAGE
Over the course of the last 500,000 years, women have been engaging in group and domestic activities including child rearing, that promoted the evolution of the neural substrates which subserve the development of human speech, including bilateral representation of language.
As detailed in chapters 10,11, and 15, language is both emotional and descriptive, grammatical and melodic, consisting of word units and prosody, such that just as both halves of the brain interact to produce music (Joseph, 1988a), both halves become activated when engaged in language related activities, the left providing the grammatical word units, the right supplying the emotional melody. Hence, as demonstrated through functional imaging, the right (as well as the left) hemisphere becomes activated (Bookheimer, et al., 1995; Bottini et al., 1994; Peterson, et al. 1988; Price, et al., 1996; Shaywitz, et al., 1995). However, the female right (and left) hemisphere appears to be superiorally endowed with these and other aspects of language (Joseph, 1993; Shaywitz et al., 1995).
Hence, human females display clear language, articulation, word knowledge, syntactic, and related linguistic superiorities over males (Bayley, 1968; Broverman et al., 1968; Harris, 1978; Koenigsknecht and Friedman, 1976; Hampson and Kimura, 1992; Harshman et al., 1983; Hyde and Lynn, 1988; Kimura, 1993; Levy and Heller, 1992; Lezak, 1983; McGlone, 1980; McGuiness, 1976; Moore, 1967), and demonstrate bilateral cerebral activation when engaged in certain language tasks as demonstrated by functional imaging (Shaywitz, et al., 1995).
In contrast to males, human females vocalize more, engage in more social speech, display superior linguistic skills, and excel over males on word fluency tests, for example, naming as many words containing a certain letter, or words belonging to a certain category. Females also vocalize more as infants, speak their first words and develop larger vocabularies at an earlier age. Their speech as children is easier to understand, they improve their articulation and grammatical skills at a faster rate, and the length and complexity of their sentences is greater than males (Bayley, 1968; Harris, 1978; Hyde and Lynn, 1988; Koenigsknecht and Friedman, 1976; Levy and Heller, 1992; Lezak, 1983; McGlone, 1980; McGuiness, 1976; Moore, 1967).
Moreover, women gravitate toward and are overwhelmingly over represented in professions requiring conversational language, such as telephone operators, directory assistants, or secretary--over 93% of those working in these fields are women (U.S. Department of Labor, 1997).
Whereas women and girls display clear language superiorities, or a greater tendency to vocalize and speak, males suffer from more language related disturbances such as stuttering (Corballis and Beale, 1983; Lewis and Hoover, 1983). Moreover, males lose language-related capabilities as they become aged, are more likely to become aphasic following stroke, and do not recover language as quickly or as fully as females.
In addition, girls learn how to read more quickly and more proficiently than males who are more likely to suffer from reading difficulties including dyslexia (Corballis and Beale, 1983). Females not only demonstrate superior reading comprehension and writing and spelling skills (Lewis and Hoover, 1983), but in 1993 the U.S. Department of Education (USDE) reported that the writing skills of a 9 year old girl in fourth grade is equal to that of a 13 year old boy in 8th grade, and in 1997 the USDE reported that "at all age levels females continue to outscore males in reading proficiency... and females of all ages have outscored males in writing." Rreading and writing are directly associated with the functional integrity of the IPL/angular gyrus (chapter 11).
Presumably, females demonstrate superior language skills because their brains are better adapted for producing temporal-sequential and social-emotional vocalizations (via the maternal cingulate gyrus), and because, as gatherers and tool makers they were not under the same constraints as the silent male hunters. Males were required to maintain long periods of relative silence -at least while hunting. Their brains adapted accordingly.
OVERVIEW: SEX DIFFERENCES, THE PARIETAL LOBE, CORPUS CALLUSM & LANGUAGE
Superior female linguistic capacities appear to be related to their evolutionary history as child bearers, gatherers, tool makers, hide preparers and so on; tasks which would require superior social-emotional capabilities (e.g. child care, socializing) and which require considerable temporal-sequential motor capability and somesthetic sensitivity which in turn is associated with Broca's area and the parietal lobule in particular.
Gathering (and to a lesser extent tool making vs hunting), is far more likely to require bi-manual activation of the hands, and thus simultaneous activation of both parietal lobes and the motor areas of the frontal lobe. These activities might also be expected to coincide with increased functional and metabolic activity in the parietal lobes, which in turn might lead to an expansion of this tissue (inferior parietal) and an increased need to intercommunicate.
In this regard it is noteworthy that the posterior portions of the corpus callosum, i.e. the rope of fibers that interconnect the right and left parietal lobes, may be thicker and larger in females than males (Holloway et al. 1994). However contrary evidence abounds (reviewed in Holloway et al. 1994). Nevertheless, as gathering and related activities are more likely to involve both hands (vs hunting and throwing with a single hand), it might be expected that the posterior (female) corpus callosum would be larger because the female right and left parietal lobe were probably simultaneously activated and utilized by females more than males for the last 100,000 or so years. On the other hand, one might equally expect that the corpus callosal interconnections linking the motor areas, particularly those involved in fine motor functioning, would be more developed in females.
Given that women have clear language superiorities and unlike males were able to frequently and continually talk and chatter, if not with other women, then their children, sisters, or mothers, and as the IPL is involved in word finding, sentence construction, and organizing Broca's area for grammatical speech production, it might also be expected that the female IPL is more involved in language production as compared to males. Again, however, the same might be said of Broca's area.
It might also be expected that the female left parietal lobe would be more resistant to aphasic disturbances as compared to males whose language representation is more sparse and fragile. In fact, males are far more likely to become severely aphasic with left parietal injuries than females, who in turn more quickly recover from similar damage (Kimura, 1993). Conversely, females are far more likely to experience expressive aphasia with damage to Broca's area than males (Hier et al. 1994; Kimura, 1993). Again, however, they are also more likely to regain expressive speech functions.
On the other hand, it may be that sex differences in severity of initial language loss in anterior vs posterior lesions may be a function of sex differences in the vasculature and the origin and/or type of debri responsible for cerebral infarcts. In this regard, although females demonstrate clear language superiorities and have more neurological space in the right and left hemisphere devoted to linguistic and expressive functions (Joseph 1993), and in fact demonstrate bilateral activation when engaged in certain verbal tasks, whereas males tend to be more unilateral (Shaywitz, et al., 1995), the exact nature and neurological foundations for these differences are certainly still open to debate.
GATHERING & WHY WOMEN LIKE TO TALK AND SHARE THEIR FEELINGS
Over the course of human evolution, and in contrast to the silent, non-communicative (or threatening) males, female mothers and female gatherers were able to freely chatter with their babies or amongst themselves. Indeed, gathering not only fostered the development of language, but like hunting for men, also served as a social activity that enabled women to interact in a socially intimate manner.
Our ancient female ancestors probably gathered in large groups of 7 or more individuals, as the typical size of a band is about 25 individuals on average. Some women were pregnant or probably carried infants which might be set on the ground here and there, or accompanied by young adolescents who would frolic about and play. Such gathering groups must have commonly been loud, noisy and very gay affairs filled with the talk of the women and the sounds of games and yells of the children. Hence, unlike the men who must remain quiet for long time periods in order to not scare off game, the women are free to chatter and talk to their hearts delight. Talking also served as a means of maintaining the location of the group so that if a gatherer or a child chanced to walk away, she (or her child) could always relocate the others by their hodgepodge of speech.
Talking thus became part of the gathering glue and served the purpose of keeping the group together and thus of bonding the group as a collective (a function similar to that performed by the anterior "maternal" cingulate gyrus). The women talked about their children, their mates, each other, and were thus exposed and allowed to expose their own feelings and thoughts to those who valued talking as much as they. As will be detailed below, for women, to socialize and be together means to talk, and to talk is a very social bonding element for women even today (Joseph 1992b; Tanner 1992); a characteristic first forged by the evolution of the anterior "maternal" cingulate gyrus and the subsequent female tendency to vocalize with her young.
However, it is also because woman has engaged in group gathering activities, accompanied by sisters, daughters, cousins, and friends, for over a million years, that "modern" westernized woman continues to feel an innate need to "gather." That is, she "shops" and derives considerable enjoyment from shopping. Over 90% of department store space is devoted to women, because of this innate female characteristic. Women may shop when they are depressed and lonely--as gathering was always a social activity-- and they may buy dozens of articles, and "cute little shoes" and other clothes that they may never wear or wear only once. She feels impelled to shop/gather. Indeed, a woman can spend hours "shopping" and might make it an all day affair. By contrast, a man will often go to the store, pick up what he needs and leaves. A woman gathers and gathers along side numerous other gathering/shopping women. Men hunt until they kill and then go home.
Women gather. Men hunt.
VISUAL-SPATIAL SKILLS OF THE SILENT HUNTER
In contrast to females where language representation appears to be bilateral, language appears to be more greatly concentrated in the left half of the male brain (Bradshaw et al. 1977; Joseph, 1993; McGlone, 1980; Shaywitz et al., 1995). For example, among males only left hemisphere lesions result in these language deficits whereas women are more likely to suffer word finding difficulty and a reduction in vocabulary with right or left hemisphere lesions (Kimura and Harshman, 1984). In contrast to the female cerebrum, the right half of the male-brain appears to be more lateralized and functionally specialized to analyze (and sequence) visual-spatial relationships (Levy, 1972, 1974; McGee, 1979; McGlone, 1980; Witelson, 1985)--perceptual functions directly related to skill at hunting.
Whereas female gatherers are free to talk to one another and their children, hunting does not promote linguistic development as the successful hunter must be silent and capable of analyzing the spatial coordinates which separate yet link him to a potential prey. These male activities do not promote speech. Wolves and wild dogs spend a considerable part of each morning and evening tracking and hunting and there is no evidence of speech among these creatures. Speech confers few advantages to a group of human hunters, who must maintain long periods of silence so as to not scare off potential game.
Aspects of hunting, however, also put a premium on parietal-temporal lobe and right cerebral cognitive development. Tracking, aiming, throwing, geometric analysis of spatial relationships, as well as environmental sound analysis, are also directly related to the functional integrity of the right half of the brain (Guiard, 1983; Haaland and Harrington, 1990; Joseph, 1988a). The right parietal area is associated with the mediation of visual-spatial perceptual functions (chapter 10), especially in males, including providing the sensory feedback which would enable a hunter to aim and throw a spear; guidance which is transferred, via the corpus callosum to the left hemisphere somatomotor areas controlling the right upper extremity.
Hence, given 500,000 years of multi-generational male experience in hunting which usually required days or even weeks of wondering hundreds of miles from the home base, present-day males therefore demonstrate superior visual spatial skills including superior maze learning, tracking, aiming, and related non-verbal abilities, as compared to females (Broverman et al., 1968; Dawson et al., 1975; Harris, 1978; Joseph, 1993, 1999e; Kimura, 1993; Levy and Heller, 1992). This includes a male superiority in the recall of geometric shapes, detecting figures that are hidden and embedded within a complex array, constructing 3-dimensional figures from 2-dimensional patterns, visually rotating and detecting the number of objects in a 3-dimensional array, and playing and winning at chess (which requires superior spatial abilities).
Males possess a superior geometric awareness and directional sense and geographic knowledge, are better at solving tactual and visual mazes or mentally manipulating spatial relations on paper, and are far superior to females in aiming, throwing, and tracking such as in coordinating one's movements in relationship to a moving target (Broverman et al., 1968; Harris, 1978; Kimura, 1993; Levy and Heller, 1992; Linn and Petersen, 1985; Porteus, 1965; Thomas et al., 1973). Only about 25% of females in general exceed the average performance of males on tests of such abilities (Harris, 1978).
As detailed in chapter 10, various aspects of mathematical ability are directly related to visual-spatial functioning, such as geometry and the sequencing of space. However, whereas the female brain has an advantage when it comes to sequencing language, the male brain is more adept at sequencing space. Hence, males are far more likely than females to be mathematical geniuses. Even when the sample consists of females who are scholastically gifted, males achieve higher scores, for example, on the math portion of the college entrance exam, and outperform females by a ratio of 13 to 1 (Benbow and Benbow, 1984).
Moreover, some of these differences are present during childhood and early adolescence and have been demonstrated in other species (Dawson et al. 1975; Harris, 1978; Linn and Petersen, 1985; Joseph, 1979; Joseph and Gallagher, 1980; Joseph et al., 1978). For example, male rats consistently demonstrate superior visual-spatial and maze learning skills as compared to females (Joseph, 1979, Joseph and Gallagher, 1980; Joseph et al., 1978). If reared in an enriched environment, males continue to outperform females, whereas enriched females perform similarly to deprived males who in turn outperform deprived females (Joseph, 1979; Joseph and Gallagher, 1980). Hence, although the environment can exert profound influences on brain, emotion, and cognitive functioning (see chapters 28-30), when subject to similar environmental influences, these sex differences are maintained. This also explains why, despite the fact that both sexes have experience with drinking from glass containers, males outperform females when asked to specify the horizontal water level in a tilted glass (Morris, 1971; Thomas et al., 1973).
In general, these and related sex differences in cognition and behavior may be reversed only if the developing brain is subject to considerable stress (thus altering steroid secretion), or if deprived of sufficient masculinizing (testicular, steroidal) hormones, and/or if the female brain is exposed to testosterone or other steroids during the critical period of sexual differentiation (Beatty, 1992; Joseph et al., 1978; Meyer-Bahlburg, 1993; Reinisch and Sanders, 1992). For example, female rats exposed to testosterone during early brain development perform similarly to males on maze learning tasks, whereas castrated-infant males later perform similarly to females (Joseph et al., 1978).
Likewise, homosexual men (whose brains, in some cases, may have been feminized prenatally, e.g. Meyer-Bahlburg, 1993) tend to perform more poorly than heterosexual men on spatial tasks and similar to females on verbal tasks (Gladue et al., 1990; however see Gladue & Baily, 1995). Moreover, human and non-human females exposed to high levels of masculinizing hormones and androgens during early brain development demonstrate superior visual-spatial skills, and are more competitive and aggressive as compared to normal females (Dawson et al., 1975; Money and Ehrhardt, 1972; Ehrhardt and Baker, 1974; Joseph et al., 1978; Reinisch and Sanders, 1992; Mitchell, 1979). As noted, hunting and the killing of prey is related to visual-spatial perceptual functioning and the tendency to behave in an aggressive fashion.
SEX DIFFERENCES IN COMMUNICATION
It has frequently been noted that many men tend to interact and compete with one another in terms of power, status, physical and intellectual dominance, wealth, and control. In contrast, it has been argued that women tend to speak and interact in a more cooperative manner, and to be more interested in issues related to the family, inter-dependence, and social intimacy (Croates, 1986; de Beauvoir, 1961; Joseph, 1992b; Stutman, 1983; Tanner, 1990). Although as a rule, such notions do not apply to all men or women, there indeed does appear to be a gender linked difference in the manner in which many boys, men, women, and girls tend to interact and speak together; and these same sex differences appear to be biological in origin, directly related to the hunting vs gathering way of life which has characterized much of human evolution, and are also seen in other primates such as chimpanzees.
As with chimpanzees, many boys tend to play in groups where there is a recognized leader and hierarchical order of followers. The leader often wins this position based on physical strength and capability, risk taking, and his ability to control or bully others. Similarly, the hierarchy of followers is arranged along these same competitive lines. When playing boys often tend to engage in sometimes very physical, aggressive games, where wrestling, tripping, and pushing each other in fun is part of the activity (Brooks-Gunn & Matthews, 1979; Eder & Hallinan, 1978; Lever, 1976; McGrew, 1979; Savin-Williams, 1980). That this is rooted in biology and not early training, however, is also indicated by the fact that male chimpanzees and other social mammals behave in a similar fashion (de Waal, 1989; Eibl-Eibesfeldt, 1995; Goodall, 1986, 1990; Wickler, 1973).
Many girls tend to play in much smaller groups or in pairs; i.e. best friends (which is equivalent to mother-baby, sister-sister). Although hierarchies also tend to form, rather than based on physical competitiveness (although that is often a factor) it tends to be based on personality, articulatory skills, and physical attractiveness; e.g. who is the "nicest," prettiest, or the most fashionably dressed (Brooks-Gunn & Matthews, 1979; de Beauvoir, 1961; Eder & Hallinan, 1978; Ekert, 1990; Joseph, 1985). It is precisely because women are also competitive (see chapter 8), that female relationships with females who are not kin, tend not to be as long lasting, as compared to male-male friendships, the exception being female-female (e.g. mother-daughter, sister-sister) kin relationships , which, however, also tend to be quite rocky at times.
In contrast to boys and men who are more likely to become involved in physically aggressive team sports where there are clear winners and losers, many young girls are more likely to engage in cooperative activities that focus on friendship, intimacy, sharing, talking, imaginativeness, and being liked. And even among female athletes, the emphasis is often on the cohesiveness and importance of the team as a mutual cooperative, whereas males often seek to emphasize their own importance and personal status and accomplishments and to belittle their competitors.
Challenges and competition between girls are more likely to be subtle and indirect, whereas cooperativeness, at least overtly, is the glue which binds them together (Eder & Hallinan, 1978; Ekert, 1990). That this is biologically based is evident in that female chimpanzees behave in an identical fashion. As summarized by De Wall (1989, p. 137): "Adult male chimpanzees seem to live in a hierarchical world with replaceable coalitions partners and a single permanent goal: power. Adult females, in contrast, live in a horizontal world of social connections. Their coalitions are committed to particular individuals whose security is their goal...for them it is of paramount importance to keep good relationships with a small circle of family and friends."
Although both girls and boys often are concerned with being the best and tend to use force in order to get their way, boys are more likely to utilize actual physical violence; a trait rooted in biology, the sexual differentiation of the male brain, and the fact that males in general, almost regardless of species are more violent and murderous than females and in fact employ violence in order to gain access to females. By contrast, females tend to use words as weapons (the proverbial "woman's tongue") and rely on males to behave aggressively for them, and employ their sexuality to manipulate men or to compete with other women.
It is important to emphasize, however, that there are numerous exceptions, as many girls are quite physically competitive and aggressive, and many boys seek close social and emotional intimacy with their best friends as well. Probably most members of both sexes, in fact, fluctuate between these various different modes of interacting.
Nevertheless, these general patterns of interaction in turn tend to color the way in which men and women interact as adults as well, including the manner in which they view the actions and even the speech of others. That is, in very general terms, men and women often tend to be concerned with different aspects of the same experience since they sometimes have different priorities.
Indeed, a recent spate of books contend that these different sex biased viewpoints affects the very way some men and women speak, such that sometimes although engaging in ostensibly the same conversation, they in fact focus on different aspects of the same shared information and emphasize features which are quite distinct (Croates, 1986; Emil & Hallinan 1978; Tannen, 1990).
Many males tend to employ speech and language as a means of imparting not only information, but as a manner of establishing status and superiority, which in turn may promote a man's ability to gain access not only to resources, but female sex partners. Indeed, it is a common male stratagem to continually probe for weakness and to make continual attacks until thwarted or power is gained. However, such fights need not always be physical but based on threat and bluff and dominance displays that entail the clever or derogatory use of language. For example, human adolescent and adult males often utilize sarcasm, teasing, verbal ridicule, verbal directives, sexual jokes, or direct insults so as to establish superiority over a rival who may whither in response to the continual verbal onslaught. Indeed, sexual remarks, sexual "jokes" and teasing are frequent among adolescents as well as "professional" men, as it is a means of establishing sexual dominanc.
Among men, comments about one another can be quite graphic and often go well beyond innuendo and include remarks as to sexual inadequacy or potency, and may go so far as to challenge other males to serve as willing sexual orifices; e.g. "Suck my dick!" Insults and sexual comments are in fact often seemingly made in fun, and although ostensibly and overtly accepted as such, they usually belie attempts to achieve dominance over other men (Joseph, 1985, 1992b, 1993; Wickler, 1973).
In fact, sexual threats, with direct exposure of an erect penis is often employed by primates in their dominance displays, whereas phallic displays are a "universal" expression among human societies (Eibl-Eibesfeldt, 1995; Wickler, 1973). Indeed, in part is because of the potentially threatening nature of the penis, that phallic aggression has crept into the vocabulary. When someone is really "pissed off" we know he is angry and we should watch out. If someone says "fuck you!" we know they are not inviting us to have sex. If someone has been "fucked", or "screwed" it is understood that they have been diminished or taken advantaged of in some manner.
Of course, males also use phallic and other forms of rough, derogatory and teasing comments in order to establish comraderie. For example, one male friend may say to another, "you still driving that piece of shit," and both will laugh. However, when a man teases, comments, or interacts with a woman on a similar level, even when it is extremely and considerably toned down, she is likely to become exceedingly offended, sometimes to the bewilderment of the man who sees his behavior as normal.
Females are much less likely to insult one another in fun, deride each other's supposed sexual shortcomings (at least while face to face) or demand in a jocular tone that other women serve them as sexual objects. Unlike some men, it is not seen as as a means of establishing rapport or dominance.
Moreover, when women engage in the seeking of status, or when they seek to put one another down (again, at least while face to face) it tends to be less confrontational, more subtle and less aggressive as ostensibly they appear more concerned with the social harmony and the establishment of mutual, friendly understanding and rapport (Hughes, 1988). They are more likely to try to smooth things over and be more artful and subtle rather than overtly or physically aggressive, even when jockeying for positions of dominance. Of course, like men, many women have no difficulty with cutting up a competitor.
Men and women thus tend to use language differently and in order to convey different messages. Although both use language in order to convey information, details and facts, many women tend to be more interested in discussing what they or others feel, what happened to them or their friends, who said what, and how various relationships are going. For many women, talk often serves as a means for maintaining intimacy and friendly interaction as well as for conveying details on business, finance, and politics and a variety of other subjects (Croates, 1986; Joseph, 1992b, Tannen, 1990). For many men, these personal details are inconsequential and of little importance.
Ginger: "That business lunch was just wonderful. Ruth was there and my boss came and we met two prospective clients. You should have seen Ruth. She was so happy after getting that big bonus, and she was wearing the most gorgeous outfit. Really quite stylish and...
Andy (yawning and picking up a newspaper): "So what happened?"
Ginger: "Put down that paper so I can tell you. Anyway, she has lost so much weight. She must really be feeling good about herself, with all the money she has been bringing in. Even Sally was impressed, and you know how Sally feels about that."
Andy: "About what?"
Ginger: "Haven't you been listening to me?"
Andy: "Yeah, sure. Business! lunch! I'm listening. Go on."
Ginger: "Anyway, and, oh, did I tell you? Sally's little boy has been getting so big. She brought these pictures. He is just so cute. And Ruth..."
Andy: "I thought this was a business lunch."
Ginger: "It was. You should have seen the look on Ruth's face when she saw those pictures. She wants to have a baby so bad...."
Andy: "What has this got to do with your job? What did your boss have to say about that?"
Ginger: "Sally is my boss!"
Andy: "And she brings pictures of her kid to show you and her clients?"
Ginger: "What's wrong with that?"
Andy: "I don't see what that has to do with your job."
Ginger: "It has everything to do with my job. If you work with people you should be interested in what is going on in their life. People don't live and work in a vacuum. What goes on at home affects their work. Haven't you've learned that ?
Andy (yawning and reaching for the newspaper): "Learned what?"
For many men, when language and talk is personal it is either viewed as irrelevant or power oriented. Indeed, it often becomes personal when they feel their status or authority may be threatened.
Jake has come home and begins to complain to his wife Ruth about a problem at work. He is very irritated and upset.
Jake: "I don't know what's wrong with my boss. He hired this new girl and she is not working out!
Ruth: "What does she look like?"
Jake: "Very ugly. Anyway, she was supposed to type this stuff and she never even got started.
Ruth: "How old is she? Is she pretty?"
Jake: "What's that got to do with anything? She's not doing her job. She was supposed to type these papers for me and she didn't do it."
Ruth: "Well, she's new. Is she married?"
Jake: "Why are you asking me all this crap? Who cares what she looks like or how many times she's been married. She is incompetent."
Ruth: "Maybe if you were nicer to her..."
Jake: "Hey! Whose side are you on? She's the one who is screwing up. Not me."
Ruth: "I didn't say you were."
Jake: "Bull shit! I don't know why I even bother talking to you. All you do is put me down."
Ruth: "Well excuse me for being curious."
Men tend to use language to describe what they are going to do and perhaps how they are going to do it to. It serves more as a form of achieving mastery over their environment and establishing their status and position in the world rather than as a means of revealing their feelings or intimate personal details about their life.
By contrast, those men who like to gossip about others and to share intimate and personal details are often shunned by other men as they are not interesting to talk to.
Men in professions where they are required to repeat information, such as television network newscaster, also tend to be somewhat or even highly effeminate (if not bisexual or homosexual) particularly in regard to vocal patterns and body language (e.g. Peter Jennings of ABC news). And these "men" tend to be dismissed as intellectual light weights, e.g. "talking heads." In fact, men who "have the gift of gab," are often viewed by other men as a "bull shitter," or even as lacking in status or as posing a possible threat as they "talk too much," or have a "big mouth."
Women are more likely than men to use language as a means of maintaining social intimacy and are much more willing or likely to interweave professional talk with friendship. Women and girls use language as a means of maintaining a relationship, of feeling close and involved. Language is the glue that binds, and women are very concerned about and interested in what other women are talking about, even if (from a man's point of view) they are talking about nothing at all. In fact, one of the highest ratings of any television network production has been consistently obtained by an ABC daytime television show, "The View" in which a group of white and black women sit around and talk (Neilsen Ratings, May, 1999).
Men are more likely to focus on accomplishing something together, or talking about the accomplishments of others such as those who won a certain football game and those who excel or need improvement in their performance. Indeed, men are more likely to utilize speech as a means of maintaining or establishing status and to leave out details concerning their emotions or personal problems. Again, this can be directly attributed to the hunting way of life where skill and male vs male competitive (and cooperative) pressures not only determined success and failure but where weaknesses were ferreted out and ridiculed.
Women tend to become more interested in the details of a person's life and in discussing the details or their own lives as well as their thoughts and feelings, whatever they may be. When women are together this tendency naturally forms a bridge that maintains their rapport. They expect to be informed. However, when women are with men, they may feel that males is acting disinterest or not being communicative and is somehow lacking in the ability to express his feelings. Indeed, it is a common complaint expressed by my female patients and in the media; supposedly men do not express their feelings and are not as communicative, at least not in the company of the opposite sex.
In fact, often the man is disinterested and is wondering why she is talking about this or that and asking him all these "irrelevant" questions. Indeed, many men tend not to share their feelings and other personal details, because to do so might put them at risk with other men, who, being so competitive, may use it against them or make fun of them. Moreover, knowing that other men are not very interested in the social and personal aspects of another man's life, even when discussing family and children, men usually keep these topics quite brief as it seems irrelevant to the task at hand; to conquer the world, make more money, get that promotion, or to discuss those who are at present conquering the world, e.g. politics and sports (Gould, 1976). These are viewed as worthy topics to discuss at length.
Even when it comes to personal difficulties, men are more likely to keep it to themselves and answer in as few words as possible. By contrast, women are more likely to not only discuss these issues at length, but to discuss it again and again with all their friends.
Andy: "So how you been getting along since that divorce?"
Jake: "You know how it is."
Many men often see no competitive advantage in discussing personal difficulties and to discuss such issues are sometimes seen as an admission of personal weakness or as a source of information that can be used to create an imbalance in power. Indeed, in my private practice, I have often heard men bitterly complain about how their spouse or girlfriend goes around telling people, including their relatives, very personal details about their relationships. Many men often view this as betraying information that is best kept secret and just between them. For them it is a breach of privacy and trust. "And its nobody g... d.... business!"
For many women, to keep these details to themselves is a breach of friendship and intimacy, for often their friends, and mothers insist on knowing the details and derive considerable enjoyment in hearing and discussing them. Again, consider Ms. Clinton revealing her husbands "emotional" problems, and "addictions" and "dysfunctions" and detailing his "emotionally abusive" childhood in a woman's magazine: TALK. Hence, women see nothing wrong or unusual about discussing or revealing intimate details about themselves or others, whereas men tend to fear they may lose power by doing so (as other men will make fun of them) and are thus so disinclined.
However, when it comes to plans, actions, and future goals, or even past conquests, the discussion between men is likely to be quite extensive, particularly if it can enhance their status.
Andy: "So getting any lately?"
Jake: "I'll say. You remember that blond that used to work at the...."
Nevertheless, even in these contexts, men are less likely to discuss what was said, how they felt about it, how romantic the evening was, how their partner felt, and so on, because it is viewed as irrelevant. They want to talk about their actions and accomplishments, whereas women tend to focus on the relationship. This of course can create considerable difficulty when men and women talk together.
Girls and women, thus tend to focus on the social, supportive, familial and the communal aspects of interaction. Men tend to focus on the individual and the struggle for dominance over the community, the family, and each other. In this regard, when women interact they tend to be less confrontational as they are more sensitive to social and emotional nuances, and as one of their main interests is to maintain the cohesion of the group or the friendship. Indeed, these same exact sex differences are also evident among other primates including chimpanzees (De Waal, 1989), and are also directly related to sex differences in the division of labor over the course of evolution, and the differential male vs female pattern of neurological development.
Again, however, it is important to emphasize that there is much variability in these seemingly differential attitudes toward the use of language as a means of social and intimate interchange. Some men are more interpersonally inclined, and many gossip among themselves about sports, politics, and each other, although they do not call it as such. Similarly, many women are much more interested in the non-personal, political, business, informational aspects of communication and would rightly take extreme exception to the notion they spend their time talking predominantly about family, relationships, clothes, shoes, sex, or each other.
From the data based on prostitution, sex differences in the infection rate for SDS, and studies of animal sexual behavior, it appears reasonable to conclude that on average, females are more sexually active and have more sexual partners, than the average male, and that they have a biological propensity to seek sex with multiple male partners. Even in the most restrictive of societies where they may be punished with death, it has been reported that some females will readily commit adultry or avail themselves of multiple sex partners who generally must be of "high status" or "handsome" (Kinsey et al., 1953; Sasson, 1992). In addition to sexuality, the human female has a greater language capacity as compared to males which in turn is related to her role as mother and gatherer.
For much of human evolution females have engaged in tasks promoting, requiring, and involving rapid temporal sequential bilateral fine-motor skills such as gathering and domestic-tool construction and manipulation. Given an innate tendency to vocalize more than males, these activities, coupled with prolonged child care and mutual child-mother vocalizations, gave impetus to the evolution of the neocortical speech areas and a female language (and social emotional speech) superiority.
In contrast to gathering groups in which females could vocalize with each other and their young, males instead pursued their own violent tendencies and became silent hunters of big game. Over the course of evolution the male proclivity to silently travel long distance in the pursuit of prey exaggerated an already innate male visual-spatial perceptual superiority.
Nevertheless, although hunting does not promote the evolution of speech, males also acquired language skills through maternal genetic inheritance and and as he had a mother who would talk to him and teach him language. Thus, like the proverbial Eve, woman the gatherer provided man the hunter with the fruit of linguistic knowledge and what would become grammatically complex, vocabulary-rich speech, language, and linguistic consciousness.